In earlier work a steric theory of DDT action has been used to design a large number of highly active DDT analogues. The basis of this theory is that a molecule of an active compound has to form a 'molecular wedge' with two distinct features. Firstly, the apex of the wedge (e.g., CCl3 group of DDT) must have a particular size and shape, and secondly, the base comprises a multiple ring structure which must have electron donating substituents. The size limitation on the base part of the molecule is less restrictive than that on the apex. It has been found that compounds synthesized to fit this model, while all possessing insecticidal activity, nevertheless exhibit considerable variations of this activity even in strictly standardized insect strains. In this preliminary study, the authors report the first results of an alternative method of correlating the activity of DDT analogues of a similar chemical structure with other molecular properties. It is assumed that any differences in this activity can be attributed to differences in electronic structure as the molecules have all been selected according to rigorous steric criteria. The results of this work were found to be promising enough to continue calculations with more compounds and more accurate molecular orbital methods.